At this time, the custom taxonomy is not supported. It does require special handling of the parms passed to the plugin as custom taxonomy is expecting an array and all parms are passed as strings or numbers.

When adding the other selection criteria which require arrays, I left the custom taxonomy off as I did not have time to test it. In 3 years, you are the first to request it and I have not needed to use it, so it is a low priority.

I am open to adding the feature to the premium version, but it will be a couple of weeks before I can focus on this.